1. Field of the Invention
The invention relates lasers that supply two or more pulses having short pulse separation and variable pulse energy among pulses.
2. Background of the Invention
Q-switched lasers are well known in the art. A Q-switch prevents lasing in a lasing medium by creating a loss in the cavity while pumping the lasing medium until a large population inversion in excess of the lasing threshold occurs. The Q-switch is then turned off and a large pulse which depletes the stored energy is obtained. When operating a Q-switched device, the time between pulses is generally at least the time required to pump the lasing medium to a sufficient population inversion to obtain a desired pulse energy when the stored energy is released by shutting off the Q-switch. Some applications require shorter pulse separation than the recovery time. Prior art devices have addressed this problem by using dual head lasers such as the Solo-PIV supplied by New Wave Research.
Efforts have been made to have variable Q-Switch operation. For example, U.S. Pat. No. 5,197,074 (Emmons) discloses a laser that it is capable of generating a laser output having preserved mode quality, waste position and output divergence as well as a selectable amplitude within a relative range of amplitudes and a selectable duration; U.S. Pat. No. 5,339,323 (Hunter) discloses the control of the laser pulse by a high loss time duration control signal supplied to a Q-switch.
There is still a need for devices which provide high energy pulses with a short pulse separation.